terça-feira, maio 18, 2004

Meteorite crater

Meteorite crater tied to mass extinction

"Scientists exploring the remains of an ancient crater off the northwest coast of Australia say they have found fresh evidence that a monster meteorite smashed into Earth about 250 million years ago and drove almost everything alive to extinction in a single spasm known as "The Great Dying."

If their evidence holds up, the scientists say, the impact would have caused the most widespread extinction episode the planet has ever experienced -- far more deadly than the fabulous crash of the object from space that killed off the dinosaurs and many other life forms 65 million years ago.

The crater was discovered years ago by geologists drilling for signs of buried oil deposits. Now, researchers say they have found evidence that the impact spread shock-fractured rocks and intriguing forms of carbon molecules across a vast area from China, India and Japan to Antarctica.

By dating the ages of the rocks, the scientists have determined that the crash must have occurred between the end of a geologic period known as the Permian, when primitive life forms were abundant, and the start of a succeeding period called the Triassic, when life quickly began recovering and evolving into ever more and larger forms." - David Perlman, Chronicle Science Editor -
Friday, May 14, 2004

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